Underdrain assembly and method of manufacturing the same

ABSTRACT

An underdrain apparatus and a method for manufacturing such apparatus are provided. The underdrain apparatus can be extruded in long sections as a unitary part to provide a light weight, strong, and easily installed underdrain assembly. The underdrain apparatus may be extruded in various sizes, shapes, and materials. Further, the underdrain apparatus may include a passageway for transporting water to and from the filter media and/or air to the filter media. In some embodiments, apertures are formed in the underdrain apparatus during an extrusion process to provide a path between the passageway and the filter media.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from U.S. ProvisionalApplication No. 61/828,577, filed May 29, 2013, the entire disclosure ofwhich is hereby incorporated by reference.

FIELD OF INVENTION

The present disclosure generally relates to water filtration systems,and more particularly, to an underdrain assembly and a method ofmanufacturing the same.

BACKGROUND

Water filtration systems are commonly employed for filtering highvolumetric flow rates of liquids, e.g., in municipal and industrialwater treatment and waste water treatment plants. Each filtration systemgenerally comprises a filter basin having a floor and vertical wallssurrounding the floor, and an underdrain assembly positioned over thefloor. A bed of granular filter media for filtering a liquid as it seepsdownward through the filter bed is placed on top of the underdrainassembly. The underdrain assembly defines a perforated false bottom inthe basin for supporting the filter media bed and for providing aplurality of fluid passageways for both removing the filtered water fromthe bottom of the filter basin and directing water and/or air into thefilter bed during backwashing.

The filter media bed is generally several feet deep and is typicallycomprised of successive layers of gravel, sand, anthracite, or othergranular filter media. The filter media bed for both traditional andgravel-less designs typically transition from coarse sizes near the topof the filter media bed to fine sizes near the bottom. Traditionalfilter designs place support media, such as multiple gravel layers, withrelatively coarse sizes between the fine filter media positioned nearthe bottom of the filter media bed and the top surface of the underdrainassembly to prevent the finer filter media from entering the underdrainapertures and contaminating the filtered water. Gravel-less filterdesigns do not use support media, but rather use various types andconfigurations of porous filters to prevent the granular filter mediafrom entering the underdrain assembly apertures.

During operation of the filtration system, unfiltered water is directedinto the filter basin to a depth of several feet above the upper layerof filter media and flows downward though the filter media bed. Duringthis filtration process, suspended materials in the unfiltered waterbecome trapped in the filter media. The water ultimately reaches thebottom of the filter bed and passes through apertures in the underdrainassembly. The water is then collected in passageways within theunderdrain assembly and is carried out of the filter basin through asuitable conduit or flume.

After the filtration system is operational for a period of time, theefficiency of the system decreases and it becomes necessary to wash thefilter media bed to remove material trapped therein. A backwashingprocess commonly is utilized to flush the filter media of trappedparticles. The backwashing process involves pumping pressurized waterand/or air in a reverse direction into the underdrain assemblypassageways, through apertures formed in the underdrain assembly, andinto the overlying filter media bed. The backwash water flows throughthe filter media bed and carries the trapped materials upward throughthe filter bed. The wash water and the materials entrained or suspendedtherein are then collected at the top of the filter basin and carriedaway.

During the backwashing operation it is desirable to obtain a uniformdistribution of wash water throughout the filter media bed to completelywash the entire filter bed. If the wash water distribution is uneven sothat dead spots occur at certain locations within the filter bed, thenthose portions of the filter bed will be improperly cleansed, therebyreducing the efficiency of the filter. The backwashing process must alsobe performed under carefully controlled conditions so as to avoid undulydisturbing or damaging the filter media bed. For example, the velocityof the wash water must be controlled at a level below that which wouldcause the filter media to become entrained in the wash water along withthe removed materials and carried away as waste. Explosive bursts ofbackwash water that open channels in the filter media, typicallyoccurring at the initiation of the backwashing cycle, must be avoided.These open channels allow unfiltered water to pass through the filtermedia without being filtered and allow finely-sized filter media to becarried away with the filtered water.

SUMMARY

Several underdrain designs have been developed over the years to addresssome of the aforementioned issues. One type of underdrain utilizes adesign in which discrete components are connected together. For example,U.S. Pat. No. 6,797,166 to Hambley et al., which is hereby incorporatedby reference in its entirety herein, discloses an underdrain apparatushaving a cover member, a water orifice member, and a bottom member,which must be connected together before operation. Further, manyexisting underdrain designs are manufactured in short discrete lengths,typically two- to four-feet, which are connected together end-to-endduring installation. The cross-sectional and end-to-end connectionjoints are prone to leakage and backwash pressure loss, thus reducingthe effectiveness of the underdrain. In addition, these designsgenerally consist of many parts that must be assembled in the filtermedia basin, which results in high production, installation, andmaintenance costs. Further, these designs typically are heavy, whichincreases the difficulty and cost of shipping and installing theunderdrains.

In addition to segmented designs, existing underdrain assembliestypically utilize porous filter media or caps which are situated on topof the underdrain system to serve as an additional filtering mechanismbefore the unfiltered water enters the underdrain assembly. These caps,commonly porous plates, are screwed into place on the top of theunderdrain or held in place with the use of gaskets. Either way,installation of the porous plates is rather difficult and inefficient,making it a time-consuming and costly procedure. In addition, after aperiod of use, the porous plates must be removed and replaced.

U.S. Pat. No. 6,740,237 to Roberts et al. (“Roberts”), which is herebyincorporated by reference in its entirety herein, attempts to solve someof the aforementioned problems. Roberts provides an extruded underdrainblock with a plurality of orifices. The underdrain blocks of Robertshave fewer components than many existing underdrain systems; however,Roberts' extruded underdrain blocks are prone to failure due in part tothe box cross-sectional design having a plurality of intersecting walls.Further, the underdrain blocks of Roberts utilize a porous plateinterconnected to the underdrain block by a separate extrusion member.The separate extrusion member is prone to failure during installationand backfill of the filter media bed prior to operation. Furthermore, inutilizing the invention disclosed in Roberts, it is necessary to staggerthe extruded underdrain blocks with structural members to furthersupport the underdrain block, which reduces the surface area of theunderdrain assembly.

In summary, many existing underdrain assemblies are heavy structures,which increase the difficulty and cost of shipment and installation.Further, existing underdrain assemblies are very complex and typicallyconsist of many parts. This complexity, from which many drawbacksresult, creates significantly high production costs as well as highcosts of labor in installing and maintaining the underdrain assembly.

Thus, there is a need to provide an underdrain assembly, and a method ofmanufacturing the underdrain assembly, that has fewer components and arelatively light weight, yet has the strength to withstand installationand operational forces, including the downward forces exerted by thefilter media bed.

The present disclosure is generally directed to an underdrain assemblyfor use in connection with a filter media bed in a liquid filtrationsystem. In various embodiments, an extruded underdrain apparatus isprovided that comprises a unitary part, thus decreasing thetransportation, assembly, installation, and maintenance costs.

One aspect of the present disclosure is to extrude an underdrainapparatus using a formable material. In an embodiment, the extrudedunderdrain apparatus is constructed of an extrudable material, which maybe selected based upon the desired shape and material properties of theunderdrain apparatus. Extrudable materials include, but are not limitedto, metals, polymers, and ceramics. Extrudable metals include, but arenot limited to, aluminum and steel. Extrudable polymeric materialsinclude, but are not limited to, polyvinyl chloride (PVC), chlorinatedpolyvinyl chloride (CPVC), high density polyethylene (HDPE), and otherthermoplastic materials. The ability to extrude the underdrain apparatusreduces assembly and installations costs, and thus is advantageous overexisting underdrain apparatus.

Another aspect of the present disclosure is to extrude an underdrainapparatus as a unitary part. In an embodiment of the present disclosure,the underdrain apparatus includes a cover member and a water drainmember extruded as a single component. In some embodiments, theunderdrain apparatus is extruded with orifices. This removes the extrastep of forming the apertures after extruding the underdrain apparatus.Additionally, this removes the necessity of plugging undesired aperturesresulting during the formation of internal apertures, as is required bymany existing underdrain processes.

Yet another aspect of the present disclosure is to extrude an underdrainapparatus in long sections, which may include lengths up to andexceeding twenty-five feet. In some embodiments, the underdrainapparatus can be extruded to match the length dimension of the filterbasin. In these embodiments, the underdrain apparatus minimizesend-to-end connection joints, thus improving the efficiency of theunderdrain assembly.

A further aspect of the present disclosure is to extrude an underdrainapparatus in various shapes. In some embodiments, extruded shapesinclude, but are not limited to, trapezoidal, triangular, rectangular,square, circular, and elliptical. In addition, in some embodiments, anextruded underdrain apparatus has a cover member and a water drainmember. In these embodiments, the cover member and the water drainmember may be extruded in various shapes, which may be different fromeach other. The extruded shape is based upon overall size, includingheight and width, weight, strength, and passageway volumeconsiderations.

Another aspect of the present disclosure is to provide an underdrainassembly including a plurality of underdrain apparatus. In someembodiments, the underdrain apparatus are interconnected togetherside-by-side to cover the floor of a filter basin. For example, theunderdrain apparatus can be welded, bonded, bolted, screwed, riveted, orinterconnected using other suitable interconnection methods known in theart. In some embodiments, multiple underdrain apparatus are extrudedside-by-side as a unitary part. In these embodiments, the underdrainassembly joints are further reduced, resulting in enhanced performanceof the underdrain assembly.

Methods for manufacturing an underdrain assembly according toembodiments of the present disclosure are also provided. In addition,methods of filtering unfiltered water through an underdrain assembly ofembodiments of the present disclosure as well backwashing a liquidfiltration system and underdrain assembly of embodiments of the presentdisclosure are provided. In some embodiments, an extrudable material isextruded in long sections to provide a light weight, strong, and durableunderdrain apparatus. In some embodiments, orifices are formed in theunderdrain apparatus during the extrusion process, thus removing thestep of drilling, punching, or otherwise forming orifices in theunderdrain apparatus after extrusion as required in existing processes.After extrusion, in some embodiments, the underdrain apparatus areinterconnected side-by-side to form an underdrain assembly that covers afloor of a filter basin.

The phrases “at least one”, “one or more”, and “and/or”, as used herein,are open-ended expressions that are both conjunctive and disjunctive inoperation. For example, each of the expressions “at least one of A, Band C”, “at least one of A, B, or C”, “one or more of A, B, and C”, “oneor more of A, B, or C” and “A, B, and/or C” means A alone, B alone, Calone, A and B together, A and C together, B and C together, or A, B andC together.

The term “a” or “an” entity, as used herein, refers to one or more ofthat entity. As such, the terms “a” (or “an”), “one or more” and “atleast one” can be used interchangeably herein.

The use of “including,” “comprising,” or “having” and variations thereofherein is meant to encompass the items listed thereafter and equivalentsthereof as well as additional items. Accordingly, the terms “including,”“comprising,” or “having” and variations thereof can be usedinterchangeably herein.

It shall be understood that the term “means” as used herein shall begiven its broadest possible interpretation in accordance with 35 U.S.C.,Section 112, Paragraph 6. Accordingly, a claim incorporating the term“means” shall cover all structures, materials, or acts set forth herein,and all of the equivalents thereof. Further, the structures, materialsor acts and the equivalents thereof shall include all those described inthe summary of the invention, brief description of the drawings,detailed description, abstract, and claims themselves.

Unless otherwise indicated, all numbers expressing quantities ofingredients, dimensions reaction conditions and so forth used in thespecification and claims are to be understood as being modified in allinstances by the term “about”.

The Summary is neither intended nor should it be construed as beingrepresentative of the full extent and scope of the present invention.Moreover, references made herein to “the present invention” or aspectsthereof should be understood to mean certain embodiments of the presentinvention and should not necessarily be construed as limiting allembodiments to a particular description. The present disclosure is setforth in various levels of detail in the Summary as well as in theattached drawings and the Detailed Description and no limitation as tothe scope of the present disclosure is intended by either the inclusionor non-inclusion of elements, components, etc. in this Summary.Additional aspects of the present disclosure will become more readilyapparent from the Detailed Description, particularly when taken togetherwith the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention andtogether with the general description given above and the detaileddescription of the drawings given below, serve to explain the principlesof these embodiments. In certain instances, details that are notnecessary for an understanding of the disclosure or that render otherdetails difficult to perceive may have been omitted. It should beunderstood, of course, that the invention is not necessarily limited tothe particular embodiments illustrated herein. Additionally, it shouldbe understood that the drawings are not necessarily to scale.

FIG. 1 is a perspective view of an extruded underdrain apparatusaccording to an embodiment of the present disclosure;

FIG. 2 is an end view of the extruded underdrain apparatus shown in FIG.1; and

FIGS. 4-8 are end views of alternative underdrain apparatus according toembodiments of the present disclosure.

DETAILED DESCRIPTION

FIGS. 1-8 generally depict embodiments of an underdrain apparatus foruse in connection with filter media systems. Referring to FIGS. 1-2, anunderdrain apparatus 10 according to an embodiment of the presentdisclosure is illustrated. The depicted underdrain apparatus 10 has beenextruded as a unitary part and generally comprises a cover member 14 anda water transport member 18. The underdrain apparatus 10 has an airpassageway 22, a water passageway 26, and an intermediary passageway 30that interconnects the water passageway 26 with the filter media bed. Insome embodiments, a porous filter may be positioned within theintermediary passageway 30 to further filter the water before it entersthe water passageway 26.

In the depicted embodiment, air orifices 34 are formed in the sides 38of the cover member 14 and are in fluidic communication with the airpassageway 22. The air orifices 34 are utilized to scour the filtermedia with pressurized air. Air scouring can improve the removal ofimpurities in the filter media, and may be utilized during waterbackwash of the filter media. As illustrated, the air orifices 34 areintermittently positioned along the length of underdrain apparatus 10.As can be appreciated, the number, size, shape, and location of the airorifices 34 may vary depending on the desired performance of the airscour operation. Additionally, the direction of the air orifices 34 maybe varied to ensure that the filter media is thoroughly scoured. Asillustrated, the air orifices 34 are formed in the sides 38 of the covermember 14 and not in the top 42 of the cover member 14. This positioningensures that the air scour operation will remove impurities in thefilter media located between adjacent underdrain apparatus 10.

Water orifices 46 also are formed in the sides 38 of the cover member 14and are in fluidic communication with the water passageway 26 viainternal orifices 50. The water orifices 46 and the internal orifices 50act as water inlets during the filtration cycle and water outlets duringthe backwash cycle. By increasing or decreasing the number and/or sizeof water orifices 46 and/or internal orifices 50, the quantity of waterpassing between the filter media and the water passageway 26 can bevaried as desired. The water orifices 46 in FIGS. 1-2 are positioned inthree parallel rows and are the same size. As can be appreciated, eachwater orifice 46 can vary in size and position.

Generally, the air orifices 34 and the water orifices 46 allow air andwater to exit on both sides 38 of the underdrain apparatus 10. As can beappreciated, the size of the orifices may be adjusted to release more orless air or water as is desirable in a particular operating environment.For example, the orifices may be smaller in certain filter beds toprevent the migration of filter media through the orifices.Additionally, the size and spacing of the orifices are dependent onpractical issues regarding hydraulic considerations, structuralcapacity, and manufacturing concerns as well as on the size and type offilter media placed on top of the underdrain. For example, designcriteria include the desired flow rate, head loss, and distributioncharacteristics.

The underdrain apparatus 10 depicted in FIGS. 1-2 also has a bottom 54that extends beyond the sides 38 of the cover member 14 to defineflanges 58. The flanges 58 may be utilized to interconnect adjacentunderdrain apparatus 10 to form an underdrain assembly. Theinterconnection between adjacent underdrain apparatus 10 can beaccomplished, for example, by adhesives, fasteners, and welding,including spot welding and ultrasonic welding.

To manufacture the underdrain apparatus 10 illustrated in FIGS. 1-2, anextrusion process is utilized. The extrusion process according to oneembodiment generally includes heating a formable material to its meltingpoint, directing the material through a die to form the desired crosssection, and maintaining the desired shape until the part has cooledenough to become dimensionally stable. In some embodiments, the airorifices 34, the water orifices 46, and/or the internal orifices 50 areformed during the extrusion process. Forming the orifices during theextrusion process eliminates the extra step of forming the orificesafter the extrusion process has been completed as is required byexisting underdrain manufacturing processes. Various process parameters,including material temperature, material flow rate, production rate,exit temperature, and cooling air flow, are controlled to properly coolthe extruded form to maintain its structural integrity.

By extruding an underdrain apparatus 10 in long sections as a unitarypart, the resulting underdrain assembly comprises fewer components andis less complex than the existing underdrain systems. For example, anunderdrain apparatus 10 may be extruded to the length dimension of thefilter basin to reduce the necessity of interconnecting underdrainapparatus 10 end-to-end. Additionally, in some embodiments, multipleunderdrain apparatus 10 may be extruded side-by-side to further reducethe number of connection joints in the underdrain assembly. By usingmaterials such as an extrudable polymeric plastic, the resultingunderdrain assembly is lighter than existing underdrain systems. Fewercomponents and lighter components make the underdrain apparatus 10easier to ship, assemble, install, and maintain. Generally, maintenancecosts are reduced because there are less components that canmalfunction.

Although not depicted, an end plate may be interconnected to both endsof the underdrain apparatus 10 to seal the ends of the underdrainapparatus 10. In some embodiments, end plates are formed out of the samematerial as the underdrain apparatus 10 and are shaped to fit thecross-section of the underdrain apparatus 10. The end plate may includean air inlet for injecting pressurized air into the air passageway 22during air scouring and a water inlet for injecting water into the waterpassageway 26 during backwashing. Additionally, the end panel mayinclude a water outlet to act as a conduit for filtered water to flowout of the filter basin during filtration. A single feature may act asboth the water inlet and the water outlet.

In operation, underdrain apparatus 10 are placed on a floor of a filterbasin. Adjacent underdrain apparatus 10 are interconnected to define anunderdrain assembly that covers the filter basin floor. Then, filtermedia is positioned on top of the underdrain assembly to define a filtermedia bed. The filter media bed is typically comprised of successivelayers of gravel, sand, anthracite, or other granular filter media.Unfiltered water is directed into the filter basin and flows downwardthrough the filter media bed, which removes impurities from theunfiltered water. The water ultimately reaches the bottom of the filterbed and passes through the water orifices 46 into the water passageway26, which transports the filtered water to a conduit which carries thefiltered water out of the filter basin.

After the filtration system has been operational for a period of time,the efficiency of the system decreases due to trapped suspensions. Toflush out the trapped impurities, filtered water is flowed through thewater passageway 26, out of the orifices 46, 50, and upward through thefilter media bed during a backwash operation. This fluidizes the filtermedia and rinses out the dislocated particles from the interstitialvoids. The backwash operation also loosens the filter media bed toeliminate packing and established flow channels. After the backwashwater is discharged, filtration is resumed. In addition to backwashingthe filter media, air scouring may be performed to further loosen andclean the filter media. During air scouring, pressurized air is flowedthrough the air passageway 22, out of the orifices 34, and into thefilter media bed.

There are many cross-sectional designs that can be extruded according toembodiments of the present disclosure. For example, FIGS. 3-6 showalternate embodiments of an underdrain apparatus 10. As shown in FIGS.3-4, an underdrain apparatus 10 includes a trapezoidal cover member 14and a trapezoidal water transport member 18. FIG. 3 depicts an invertedtrapezoidal water transport member 18, which decreases the size of thewater passageway 26 and increases the size of the intermediarypassageways 30. FIG. 4 depicts a trapezoidal water transport member 18,which increases the size of the water passageway 26 and decreases thesize the intermediary passageways 30. Referring to FIG. 5, an underdrainapparatus 10 includes a triangular cover member 14 and a trapezoidalwater transport member 18. The triangular shape of the cover member 14eliminates the filter media from laying on a top surface of theunderdrain apparatus 10. Referring to FIG. 6, an underdrain apparatus 10includes a trapezoidal cover member 14 and a circular water transportmember 18. As depicted in FIG. 6, the water transport member 18 isintegrally extruded with the sides 38 of the cover member 14. In analternative embodiment, the water transport member 18 may be integrallyextruded with the top 42 of the cover member 14 as well, thus splittingthe air passageway 22 into two passageways. In this alternativeembodiment, the water transport member 18 provides additional stiffnessto the top of the cover member 14.

FIG. 7 illustrates another embodiment of an underdrain apparatus 10. Asdepicted, the underdrain apparatus 10 includes a trapezoidal covermember 14 with a flange 58 and a circular water transport member 18. Thecover member 14 and the water transport member 18 are not extruded as aunitary part. Rather, the cover member 14 and the water transport member18 are formed prior to assembly and ultrasonically welded together toprovide a seal between the air passageway 22 and the intermediarypassageways 30. In some embodiments, the cover member 14 is constructedof a different material than the water transport member 18. For example,the cover member 14 may be constructed of stainless steel and the watertransport member 18 may be constructed of polyvinyl chloride.

FIG. 8 illustrates an embodiment of three underdrain apparatus 10extruded as a unitary part. As discussed above, embodiments of thepresent disclosure can be extruded in relatively long sections, up toand exceeding twenty-five feet, to reduce the necessity of joiningsuccessive underdrain apparatus 10 in an end-to-end fashion. Asillustrated in FIG. 8, another embodiment of the present disclosureextrudes a plurality of adjacent underdrain apparatus 10 as a unitarypart. This reduces the necessity to join adjacent apparatus 10 in aside-to-side fashion. Further, as discussed above, in some embodimentsthe orifices may be formed during the extrusion process. Thus,embodiments of the present disclosure provide an underdrain apparatus 10that reduces the assembly, installation, and maintenance costs ofexisting underdrain assemblies. Further, various cross-sectional shapescan be extruded to achieve a light weight, yet durable underdrainapparatus 10 that can withstand the weight of a filter media bedpositioned on top of the underdrain apparatus 10.

The present disclosure has been presented for purposes of illustrationand description, and is not intended to be exhaustive or limiting. Inaddition, while various embodiments, configurations, and/or aspects ofthe present disclosure have been described in detail, it is apparentthat modifications and alterations of those embodiments, configurations,and/or aspects will occur to those skilled in the art. For example,while the flowcharts have been discussed and illustrated in relation toa particular sequence of events, it should be appreciated that changes,additions, and omissions to this sequence can occur without materiallyaffecting the operation of the disclosed embodiments, configuration, andaspects. Further, while various features have been grouped together inone or more embodiments, configurations, and/or aspects, it should beappreciated that these features may be combined in alternateembodiments, configurations, and/or aspects other than those discussedabove. Moreover, references made herein to “the present invention” oraspects thereof should be understood to mean certain embodiments of thepresent invention and should not necessarily be construed as limitingall embodiments to a particular description. It is to be expresslyunderstood that such modifications and alterations are within the scopeand spirit of the present invention, as set forth in the followingclaims.

What is claimed is:
 1. An underdrain apparatus comprising: a firstgenerally planar surface; a second generally planar surface adjacent atleast a first side of the first generally planar surface; a thirdgenerally planar surface adjacent to at least a second side of the firstgenerally planar surface; a substantially cylindrical body bounded bythe first, second and third generally planar surfaces and adjoined to atleast the second and third generally planar surfaces; a plurality oforifices extending in a longitudinal direction about at least one of thefirst, second and third generally planar surfaces; wherein theunderdrain apparatus is formed of a formable material; and wherein theunderdrain apparatus is formed by extrusion.
 2. The underdrain apparatusaccording to claim 1 wherein the angle formed between the firstgenerally planar surfaces and the second generally planar surface andthe angle between the first generally planar surfaces and the thirdgenerally planar surface is an obtuse angle.
 3. The underdrain apparatusaccording to claim 1 further comprising at least a fourth generallyplanar surface adjacent to at least a portion of the second and thirdgenerally planar surfaces.
 4. The underdrain apparatus according toclaim 1 wherein the substantially cylindrical body further comprises aplurality of orifices about a longitudinal direction of thesubstantially cylindrical body.
 5. The underdrain apparatus according toclaim 1 wherein the formable material is selected from the groupconsisting of a metal, a polymer, a ceramic material, an aluminummaterial, a steel material, a polyvinyl chloride (PVC), a chlorinatedpolyvinyl chloride (CPVC), a high density polyethylene (HDPE), and athermoplastic material.